P123 Identifying differences in sleep spindle activity in children with excessive daytime sleepiness

Abstract Background Sleep spindles have been hypothesised to protect the sleeping brain from external stimuli and thus promote sleep. We aimed to identify differences in sleep spindle activity between children with narcolepsy, idiopathic hypersomnolence (IH) and subjectively sleepy children (with a normal multiple sleep latency test), and if there was any association between spindle activity with quality of life or severity of daytime sleepiness. Methods Spindles were manually identified from both C4 and F4 EEG signals during N2 and N3 sleep in 25 children with narcolepsy, 6 with IH and 21 with subjective sleepiness. Spindles were classified as Fast or Slow. Spindle activity was characterised as number, average duration (s), density (spindles/min) and intensity (density x average duration). Parents completed OSA-18 and ESS-CHAD questionnaires. Results Both F4 and C4 Slow and Slow&Fast spindle durations were longer in children with narcolepsy (p<0.001) and IH (p<0.05) compared to subjectively sleepy children. In the subjective sleepy children, all activity measures for all C4 spindles were negatively correlated with emotional symptoms and C4 Slow spindle density and intensity were negatively correlated with sleep disturbance on the OSA-18. Duration of C4 Fast spindles was positively correlated (p<0.05) with the ESS-CHAD score. Conclusions The increased duration of frontal and central spindles in children with narcolepsy and IH likely represents an attempt to stabilise sleep during NREM. Our preliminary finding of a relationship between reduced spindle activity and daytime symptoms requires further assessment with questionnaires tailored to children with excessive daytime sleepiness.